I've experienced some of these things but not in a gunfight. Probably most of you have, too, but don't realize it because you're only thinking of gunfighting. Probably you've had extremely stressful and sudden situtations when driving that approximate somewhat the stress of shootings. Of course, you are also schooled to think of a gunfight as a kill or get killed situation but not so when you're driving (I assume).

I think reactions might be unpredictable for an individual, but hopefully less so when they've been through a certain kind of situation before. Likewise, none of this has to be a sudden thing. By that I mean only that the stressful situation might be something that lasts--for minutes--or even hours. That sort of takes it to a new level but that's outside of my experience. But there's nothing that says an emergency will be over in five or ten minutes.

Some of this discussions revolves around exactly what you mean when you say "tunnel vision." It's still a good term though but even when you've done something that results in what you think of as tunnel vision, it's still hard to describe. I would say that it does seem like things slow down but as PH/CIB (Purple Heart etc?) says, what really happens is that you are speeding up, sensory-wise. Most of the time things happen and you're barely aware of them. But in an emergency, you (hopefully) will perform a little better.

I've never heard of the expression tunnel hearing but I think I understand what is meant. I have heard a nearby gunshot unexpectedly and heard no more than a pop. Yet other times a car horn might startle me. I can't explain it but at least hardly anyone blows their horn anymore.